///集合取交集Array.intersect = function () { var result = new Array(); var obj = {}; for (var i = 0; i < arguments.length; i++) { for (var j = 0; j < arguments[i].length; j++) { var str = arguments[i][j]; if (!obj[str]) { obj[str] = 1; } else { obj[str]++; if (obj[str] == arguments.length) { result.push(str); } } } } return result;}//集合去掉重复Array.prototype.uniquelize = function () { var tmp = {}, ret = []; for (var i = 0, j = this.length; i < j; i++) { if (!tmp[this[i]]) { tmp[this[i]] = 1; ret.push(this[i]); } } return ret;}//并集Array.union = function () { var arr = new Array(); var obj = {}; for (var i = 0; i < arguments.length; i++) { for (var j = 0; j < arguments[i].length; j++) { var str=arguments[i][j]; if (!obj[str]) { obj[str] = 1; arr.push(str); } }//end for j }//end for i return arr;}//2个集合的差集 在arr不存在Array.prototype.minus = function (arr) { var result = new Array(); var obj = {}; for (var i = 0; i < arr.length; i++) { obj[arr[i]] = 1; } for (var j = 0; j < this.length; j++) { if (!obj[this[j]]) { obj[this[j]] = 1; result.push(this[j]); } } return result;};console.log(Array.intersect(["1", "2", "3"], ["2", "3", "4", "5", "6"]));//[2,3]console.log([1, 2, 3, 2, 3, 4, 5, 6].uniquelize());//[1,2,3,4,5,6]console.log(Array.union(["1", "2", "3"], ["2", "3", "4", "5", "6"], ["5", "6", "7", "8", "9"]))console.log(["2", "3", "4", "5", "6"].minus(["1", "2", "3"])); const arr1 = [1,2,3,4];const arr2 = [3,4,5,6];const arr3 = [1,2,3,2,1,3,4];let s1 = new Set(arr1);let s2 = new Set(arr2);//并集let union = [...s1, ...s2];console.log(union); //[1, 2, 3, 4, 3, 4, 5, 6]//交集let intersect = arr1.filter( x => s2.has(x) );console.log(intersect); //[3, 4]//差集let difference = arr1.filter( x => !s2.has(x) );console.log(difference); //[1, 2]//去重let minus = [...new Set(arr3)];console.log(minus); //[1, 2, 3, 4]
